Springs manufactured from elastomer materials are well known in the art. Such springs typically have a cylindrical shape and are directed to applications requiring very high spring rates for absorbing substantial quantities of energy in applications such as are associated with the railcar industry. In addition, such known springs are designed to absorb energy directed axially against one or both ends of the spring.
Elongated springs which are curved have broad and varied applications and are commonly used to absorb and return energy. Typically, with this type of spring, the load is generally applied to an apex of the curved spring and one or both of the longitudinally spaced ends thereof are confined against longitudinal expansion.
It can be beneficial if the spring can be adjusted to affect the spring rate. It is difficult to predict the exact conditions and stresses to which such a spring will be subjected. The fatigue life of most curved springs, however, is generally limited, thus, increasing the required maintenance of the apparatus with which the spring is arranged in operable combination.
Depending upon their application, most curved springs are loaded not only vertically but also by horizontal forces and torques in the longitudinal vertical and transverse vertical planes. Such forces can be generated in several different modes of operation which, again, are highly dependent upon the particular spring application. The stresses induced in the spring can be quite high. In some applications, the spring is required to offer a first spring force or first resistence when operated in one direction and a second spring force or second resistence when operated in a second direction. Moreover, the spring must be capable of operating under repetitive and extended cyclic operations.
In view of the above, and in accordance with the present invention, there is a continuing need and desire for an elastomeric spring capable of offering a first spring force or first resistance when operated in one direction and a second spring force or second resistence when operated in a second direction and which offers substantially constant repetitive operating characteristics with no significant deterioration during operation.